Specifically Target Impurities to Isolate Desired Product

Polymer Supported Scavengers

Polymer scavengers are functionalized polymers that are designed to react with and bind excess reagents and by-products, facilitating their removal by simple filtration. Similar to supported scavengers, their application is very simple:

Add resin/silica to reaction

Stir for desired time

Filter as usual to purify

...or pack them into columns and flow through for fixed-bed applications. There are numerous applications – from reaction clean-up to catalysis, from catch and release purification to solvent switching, to trace transition metal removal from APIs.

Polymer Types

Biotage® uses two different resin types for its scavengers, 1% crosslinked poly(styrene-co-divinylbenzene) and highly crosslinked, macroporous polystyrene. The 1% crosslinked polystyrene is designated by PS-. MP- designates highly crosslinked, macroporous resin. Highly crosslinked macroporous resins swell significantly less in solvent and they are not dependent on swelling to be effective. Instead, reagents diffuse through the pore structure to reach reactive sites. For this reason, MP- resins can be used in confined volumes where swelling would be a problem. They can also be used with a much wider variety of solvents.

Non-Toxic, No Smells and Easier To Handle

Once bound to the resin (or silica) there vapor pressure of volatile or toxic reaction components is virtually eliminated so bound resins and silica scavengers are especially good for capturing compounds such as isocyanates, or nucleophilic amines/anilines.

Drive Reactions with Excess Scavenger

Adding more reagents will drive a reaction to completion, but the excess reagents will need to be separated afterwards, involving additional purification steps. With a resin bound strategy, the resin (or silica) is heterogeneous, it does ‘see’ the solution, but it is completely insoluble, so removing excess after the reaction is just a case of filtering using simple and inexpensive laboratory equipment.

Re-cycle and Re-use

Being easy to recover after a reaction, some supported scavengers are compliant with principles of green chemistry. Ion-exchange mechanisms for example, catch and release purification is a great example of this. While many resins are used once, for reasons of industry preference or regulation, Biotage can support clients who need guidance on how to re-use, by providing technical guidance.

Making the Impossible – Possible

Resins and silicas are heterogeneous, meaning that we can lock away products and completely selectively release them later (or lock away by-products, and only let product through). Processes that are energy and labor intensive, such as solvent switching, can be achieved in a matter of seconds at room temperature and at normal atmospheric pressure. High boiling point solvents such as DMF and DMSO can be removed from amine mixtures and replaced with more volatile solvents.

Thermally and Mechanically Stable

Resin scavengers work well with overhead stirring or mechanical shaking. They withstand temperatures up to approx. 150 °C (i.e. microwave chemistry heating conditions). Silica supported scavengers are mechanically stable, and may also be stirred but are more often packed into fixed bed formats for flow through applications. Silicas can withstand 150–200 °C temperatures, so as long as the intended chemistry is compatible, the resin or silica option is an efficient delivery vehicle for the chemistry of the project.

Scale-Up and Formats

Additionally, Biotage has a flexible cartridge packing facility to accommodate many scale-up paths and options, from grams to multi-kg and in a variety of formats for processing.

Long Shelf Life

Polymer supported scavengers are stable. By definition they only take part in the reactions they were designed for, so side-reactions and degradation is much less of an issue compared to small molecule chemistry. In real terms the shelf-life of a functionalized polymer may be indefinite, so we recommend a nominal 1 year expiry when the product is stored in cool dry conditions.

Q&A

Removing Ions from Peptides

Q:

I need to remove counter ion from peptidic molecules. Can I use PS-Trisamine to achieve this?

A:

This will depend on the counter ion and peptide in question, and the state of protection/deprotection. A couple of scenarios are:

1) If the goal is to remove anions from a cationic peptide structure, then PS-Trisamine will only work in organic solvents.

2) If the solvents are aqueous or non-swelling, then MP-Trisamine may be useful. The better solution is Si-Carbonate or MP-Carbonate.

3) If the goal is remove cationic from a anionic peptide structure, then SCX-2 or MP-TsOH would be more helpful.

About Biotage

Biotage is a global Life Science company that develops innovative and effective solutions for separation within organic and analytical chemistry, as well as for industrial applications. Biotage is listed on NASDAQ Stockholm.